Make Semver really optional and allow disabling of tests

[jlmxyz]

• the find_package(mbits-semver fails because it's tagged as required => make it optional
• added options to build tests
• removed python (there is only C++ and CMake source code... why python is required here? might be required by some dep, but it's the dep that should manage the requirement)
• CONAN_CMAKE_SILENT_OUTPUT => unused....
• make Makefiles verbose by default
• added compile.json generation for user using COC.nvim and other clangd based code browser/completion